helloworld.go - How to run GoLang Sample Code using the Hello World API and Mutual SSL

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Visa Employee

helloworld.go - How to run GoLang Sample Code using the Hello World API and Mutual SSL

In this "How-to" guide we will show you how to run the “Hello World” project using Visa Hello World API and Two-Way SSL (Mutual Authentication). The Hello World API is a simple API for testing the connectivity with the Visa Network.


Important Links:



How to Create a Visa Developer Project


Before you are able to run the “Hello World” Project, you must create a Visa Developer Portal (VDP) project and get credentials. If you haven't registered yet just click on register here, fill out the account information, agree to the terms and conditions and click on receive emails. Once you have successfully activated your account, you will see your dashboard and you are ready to go.




Once you are there, click on create your first project if this is your first project.  On the next page, you will be asked for details, such as project name, description and a list of APIs to choose from.




For this tutorial, we're going to select “Visa Direct” and click create project.





How to get Credentials


After creating your project, you will be redirected to the project summary page. You can obtain your project credentials by browsing the left side navigation menu of your project and click on “Credentials”.




What is required for the Two-Way SSL (Mutual Authentication)?


To be able to make an API call with 2-way SSL authentication, you need to have the following:


  1. User ID
  2. Password
  3. Your client cert
  4. Your private key previously downloaded
  5. Visa Development Platform Certificate




You will need to download the project certificate as well as the common certificates - Visa Developer Platform certificate and DigiCert Certificate and save them in the correct directory. 



How to run the GoLang Sample code of the “Hello World API” using GoLand



Next, we'll show you how to run the GoLang sample code of the “Hello World API” using GoLand. GoLand is a cross-platform IDE that provides consistent experience on the Windows, macOS, and Linux operating systems, and can be downloaded using below link:




In GoLand, a project helps you organize your source code, tests, libraries that you use, build instructions, and your personal settings in a single unit.



Step 1 - Launch GoLand


  • On the GoLand Welcome Screen, click Create New Project.




Otherwise, from the main menu, select File | New | Project


Step 2 - In the New Project wizard, select Go from the list on the left, provide the project Location, Go SDK and click Create.







Step 3 - Create a new Go file as Simple Application and named it “helloworld





Step 4 - Copy the below sample code to the “helloworld.go” file


  • Install all the required dependencies when prompt.
  • Set the below parameters:


username = "<YOUR USER ID>"

password = "<YOUR PASSWORD>"


clientCertificateFile    = "<YOUR CLIENT CERTIFICATE PATH>"

clientCertificateKeyFile = "<YOUR PRIVATE KEY PATH>"

caCertificateFile        = "<YOUR CA BUNDLE CERTIFICATE PATH>"





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package main

import (

var (
   visaUrl = "https://sandbox.api.visa.com/vdp/helloworld"

   // THIS IS EXAMPLE ONLY how will user_id and password look like
   // userId = "1WM2TT4IHPXC8DQ5I3CH21n1rEBGK-Eyv_oLdzE2VZpDqRn_U";
   // password = "19JRVdej9";
   username = "<YOUR USER ID>"
   password = "<YOUR PASSWORD>"

   // THIS IS EXAMPLE ONLY how will cert and key look like
   // clientCertificateFile = 'cert.pem'
   // clientCertificateKeyFile = 'key_83d11ea6-a22d-4e52-b310-e0558816727d.pem'
   // caCertificateFile = 'ca_bundle.pem'

   clientCertificateFile    = "<YOUR CLIENT CERTIFICATE PATH>"
   clientCertificateKeyFile = "<YOUR PRIVATE KEY PATH>"
   caCertificateFile        = "<YOUR CA BUNDLE CERTIFICATE PATH>"

func main() {

   //Load CA Cert
   clientCACert, err := ioutil.ReadFile(caCertificateFile)
   if err != nil {

   //Load Client Key Pair
   clientKeyPair, err := tls.LoadX509KeyPair(clientCertificateFile, clientCertificateKeyFile)

   clientCertPool, _ := x509.SystemCertPool()
   if clientCertPool == nil {
      clientCertPool = x509.NewCertPool()


   tlsConfig := &tls.Config{
      Certificates: []tls.Certificate{clientKeyPair},
      RootCAs:      clientCertPool,

   transport := &http.Transport{
      TLSClientConfig: tlsConfig,

   client := &http.Client{Transport: transport}
   request, err := http.NewRequest(http.MethodGet, visaUrl, nil)
   if err != nil {
   request.SetBasicAuth(username, password)
   resp, err := client.Do(request)

   if err != nil {

   defer resp.Body.Close()
   body, err := ioutil.ReadAll(resp.Body)
   log.Println("Response Status:", resp.Status)
   log.Println("Response Body:", string(body))





Step 5 - Compile Your Code 


  • Simply right click and run “go build helloworld….”





Want more? Join the Visa Developer Community to get alerts on the latest tutorials, guides and new developer resources. Stay tuned for more in the series. 


Written by: @shameem@jmedlen, & @mprsic 

Regular Visitor

Re: helloworld.go - How to run GoLang Sample Code using the Hello World API and Mutual SSL

Please detail how to get caCertificateFile        = "<YOUR CA BUNDLE CERTIFICATE PATH>" aka ca_bundle.pem

I get "x509: certificate signed by unknown authority" message if use VDPCA-SBX.pem file

Visa Employee

Re: helloworld.go - How to run GoLang Sample Code using the Hello World API and Mutual SSL

Hi @vorlenko_fb ,


Thank you for trying out the "How to" guide for GoLang. 


Please note that you will also need to download the common certificates i.e. the Visa Developer Platform certificate and DigiCert Certificate (which is the root certificate or the certificate authority and concatenate them in one file also known as bundle. 


Please see section "What is required for the Two-Way SSL (Mutual Authentication)?".


I hope I have answered your question. Let us know how it works out.


Thank you. 

Regular Visitor

Re: helloworld.go - How to run GoLang Sample Code using the Hello World API and Mutual SSL

I converted DigiCertGlobalRootCA.crt to DigiCertGlobalRootCA.pem as

openssl x509 -inform der -in DigiCertGlobalRootCA.crt -outform pem -out DigiCertGlobalRootCA.pem

and then build two bundle

cat .\VDPCA-SBX.pem > server1.pem

cat .\DigiCertGlobalRootCA.pem >> server1.pem


cat .\DigiCertGlobalRootCA.pem > server2.pem

cat .\VDPCA-SBX.pem >> server2.pem

both give me old error.


Could you give more details?

Regular Visitor

Re: helloworld.go - How to run GoLang Sample Code using the Hello World API and Mutual SSL

copy "VDPCA-SBX.pem" + DigiCertGlobalRootCA.pem server1.pem


fix the problem. Thank yoy for information